The bearings on this wheel require a 30M diameter bolt. I used a 100mm long bolt from Fastenal, along with two nuts, and some welding and fabrication work on my part to get this wheel mounted. I was able to mount the wheel to a piece of 1/4" plate that was welded to a piece of 1 1/2" square steel tubing that fit in my grinder. I put the nuts on either side of the 1/4" plate and in that way I used one of the nuts for a spacer which moved the wheel in line with the other wheels on the grinder. Fastenal has these nuts and bolts available, but they are pricey. I bought two wheels, and two nut/bolt set ups for the same price as the grinder company wanted for one wheel with a smaller axel bolt and no 1 1/2" square steel arm to mount it to. I spent $250 for two wheels and all the hardware to get them mounted. The grinder company wanted $275 for just the wheel without any hardware to mount it to the grinder with. I wish I could find the bolts at a cheaper price because I would definitely buy more wheels if I could. Both of wheels I bought on Amazon are working great at this time.